In particular for automobile applications, power conductors are sought, which can safely, and within the smallest possible space, switch the high currents that flow, for example during start of a motor. Until now, this purpose has been met with power switches fixed on a base plate or a heat sink via an intermediately located substrate. Internal connections are realised by means of so-called bonded wires. A plastic housing accommodates connections, by means of which the module is connected to externally arranged cables.
In the state of the art, power conductors usually further consist of at least one semiconductor (transistor, diode or similar elements). For long-lived and temperature-stressed component groups the power semiconductor(s) is/are preferably joined on a substrate by sintering of silver layers. Such a low-temperature connection is mentioned in the DE 10 2008 035 993 A1 as an alternative.
In this connection, the substrate can be made as a punched metal grid or as a ceramic conductor plate with one or two-sided metal coatings for the current and heat transport. For the required function of the power component group, further, passive components, such as temperature sensors, chip compensating resistors, resistor and/or capacity elements and/or shunt resistors for current measuring, are required.
Typically, these components are inserted according to methods of traditional manufacturing techniques (gluing, soldering). In this connection, the prevailing designs are the surface mounted SMD-components (surface mounted devices), which can be either glued or soldered onto the substrate.
The geometries of these passive components are adapted to these manufacturing techniques and preferably utilise the meniscus formation of the joining glue (conducting glue) or the soft solder for electrical contact formation and mechanical fixing. In this connection, the components are usually cylindrical, however, at least provided with undercuts, which could cause damage or demolition during the pressing process of the sintering. The contacts of the SMD-components on the other hand are usually metallisations at both end covers, each circumferential. A thermally contacting and at the same time electrically isolatable mounting is not possible.
Further, in the power-electronic substrates a relatively thick conductor path layer is available, which is, with common SMD-components, separated from the active component by means of a (etched) groove. The grooves of the power conductor paths usually have a width of about 60 μm to 1000 μm and sometimes also more.
Manufacturing etched grooves will usually result in a groove width whose smallest dimension is the groove depth. With ceramic conductor plates of the type DCB (direct copper bonded) the structuring process of the copper conductor path, for example with the thickness of 380 μm, will also result in a groove width of at least 380 μm to 600 μm.
Substrates can basically be all commonly used conductor plates: ceramic core conductor plates (DCB), metal core conductor plates (IMS, insulated metal substrate), organic circuit carriers (for example epoxy resin core or poly imide core conductor plates).
However, this groove width is not suited for a safe bridging by SMD components and pressure sintering techniques. The following disadvantages and process incompatibilities occur:                The circumferential end cover metallisations of the classic SMD-components require their own island contact faces within the faces of the power conductor paths. This reduces the required current carrying cross-section and the heat dissipation ability, as the heat flow will be stopped at the etched groove. Additional, cost intensive substrate surface will be required.        For technology reasons, the groove width is relatively large and the sintering pressure breaks the bridging components.        With temperature sensors of the classic design, the required island formation of the good conducting conductor path layer in the conductor path layout provides an additional thermal insulation and unduly reduces the response speed and the desired mirroring by the measured temperature of the transistor temperature.        If, on the one hand, the power semiconductors are mounted by sintering, and the passive temperature sensors are mounted during a second step by soldering or gluing, the manufacturing and quality costs will be at least doubled. Soldering of the passive temperature sensor will require an additional manufacturing step “fluid cleaning” that requires a substantial amount of energy and stresses the environment.        